RESIDENT EVIL 5

Pretty self explanatory. Easily done as a first playthrough and selecting 'Normal' at the difficulty selection screen.

This stacks with higher difficulties (professional difficulty is unlocked upon completion of veteran difficulty, or can be accessed by invitation of someone who has it unlocked already)

I found it best to complete the story on amateur to gain access to the weapons, and then do a run through with the infinite rocket launcher (gained by completing the story in under 5 hours; easy) and an infinite ammo Magnum (by upgrading one fully and buying the appropriate infinite ammo in the bonus features menu)

You do not need to do all chapters in one sitting, nor in order. You can see which missions have been completed at each difficulty; if there is a time, it has been completed.

Happy unlocking :)